There was another thread on this over in the discussion club, and I'll more or less repeat what I said there.
While it is true that there may be some advantage going male->female over other women in terms of skeletal structure (a person won't shrink and their hips won't turn after gender reassignment), it's less of an advantage in terms of musculature. Once the person has been on hormone therapy, she will atrophy until her her muscle profile matches other women's.
I see no problem with allowing trans women to compete in women's sports, as long as the person in question has been undergoing hormone therapy for a while and continues to do so.
Also, the concern that someone would change genders just to become a star athlete seems incredibly cynical and disingenuous.
I don't have the source anymore but this is pretty much true and what the researchers concluded back when people were wondering over that trans long distance runner.
Basically, testosterone is directly related to muscle mass and you need it constantly. Normal women produce a smaller amount from the ovaries.
If a M2F gets the gonads cut off so they don't produce any at all, they end up being even weaker than a regular woman on average because they'll lose all that muscle from before but it's a process and takes ~2 years to happen.
They do end up with bigger bones on average but less muscle if they have the surgery so they would kind of be terrible at sports that require quickness but have a slight advantage in activities that require mass. So, they'd kind of be like a lumbering and weakened ox. They're taking estrogen shots or whatever so they'd have even less testosterone than a normal woman because they lack the smaller amount from the ovaries.
It's why the IAAF will allow trans to compete but they have to be post-op (i.e. absolutely zero testosterone production in the body) and they have to sit for a few years to even out their muscle mass. Then, they're allow to compete. Of course, then they generally are terrible at sports at the highest level so it becomes mostly a non-issue.